1. Field of the Invention
The present invention relates to a speaker apparatus for use with various acoustic devices, visual devices and the like, for example.
2. Description of the Related Art
FIG. 1 shows an example of a speaker apparatus according to the related art. As shown in FIG. 1, this related-art speaker apparatus includes a dome-like acoustic diaphragm 121 at its center. A diaphragm having a curvature R in cross-section or a straight-line-like edge is formed from the side edge of this acoustic diaphragm 121.
A plate 126 is provided on a magnet 124 and a voice coil 123 is formed so as to have a gap 127 between it and a pole piece 125. Then, a bobbin 122 of the voice coil 123 is fixed to the acoustic diaphragm 121.
Accordingly, when a signal is inputted to a signal input line 128, the voice coil 123 is vibrated in the upper and lower direction by electromagnetic force applied to a current flowing through the voice coil 123 in a magnetic field generated by the magnet 124. Concurrently therewith, the acoustic diaphragm 121 is actuated to produce audio-frequency vibrations. FIG. 1 shows a conductive type speaker as an example of the related-art speaker apparatus.
In the case of the conductive type speaker, for example, in order to drive this diaphragm, as shown in FIG. 2 which illustrates a method of bonding a conductive type speaker diaphragm and a voice coil bobbin, a voice coil 138 is wound around a cylindrical bobbin 137 having a uniform diameter, and a front end of the bobbin 137 is bonded to a dome-like inner peripheral edge portion 133 of a dome-like diaphragm 132 of a diaphragm 131 by an adhesive agent 139.
This diaphragm 131 is fixed to a suitable means such as a frame, not shown, from a side edge of the dome-like diaphragm 132 through a joint flat portion 134 by a diaphragm side edge 136 of an edge-like diaphragm 135 having a curved-line-like cross-section or a straight-line-like cross-section.
On the other hand, in the case of a conductive type electromagnetic induction speaker, as shown in FIG. 3 which illustrates a method of bonding a conductive type electromagnetic induction speaker diaphragm and a voice coil bobbin, a conductive one turn ring 148 is fixed around a cylindrical bobbin 147 having a uniform diameter, and a front end of the bobbin 147 is bonded to a dome-like diaphragm inner peripheral edge portion 143 of a dome-like diaphragm 142 of a diaphragm 141 by an adhesive agent 149.
Alternatively, as shown in FIG. 4 which illustrates a method of bonding a conductive type electromagnetic induction speaker diaphragm and a conductive one turn ring, a front end of a cylindrical conductive one turn ring 157 having a uniform diameter is bonded to a dome-like diaphragm inner peripheral edge portion 153 of a dome-like diaphragm 152 of a diaphragm 151 by an adhesive agent 158.
As shown in FIG. 1, the conductive type speaker and the conductive type electromagnetic induction speaker are each comprised of a magnetic circuit including a permanent magnet (magnet 124) and the magnetic gap 127. The voice coil 138 shown in FIG. 2 or the conductive one turn rings 148, 157 shown in FIGS. 3 and 4 are held within this magnetic gap 127.
Accordingly, as shown in FIG. 2, when a signal current flows through the voice coil 138, the diaphragm 131 is vibrated to output acoustic energies.
Alternatively, as shown in FIGS. 3 and 4, when an induced current of a signal current flows through the conductive one turn rings 148, 157, the diaphragms 141, 151 are vibrated to output acoustic energies.
However, in the above related-art speaker apparatus, the diaphragms 131, 141, 151 including the dome-like diaphragms 132, 142, 152 and the edge-like diaphragms 135, 145, 155 are each manufactured by integrally molding a thin metal sheet such as an aluminum sheet and a titanium sheet or a polymer sheet, and the like. As a result, since the metal sheet or the polymer sheet and the like is pulled in both directions, it is unavoidable that the joint flat portions 134, 144, 154 for joining the dome-like diaphragms 132, 142, 152 and the edge-like diaphragms 135, 145, 155 are reduced in thickness.
When the voice bobbins 137, 147 or the conductive one turn ring 157 are bonded to the diaphragms 131, 141, 151 by the above related-art bonding methods and an acoustic signal is inputted to the speaker apparatus, at a certain frequency, the dome portions and the edge portions are vibrated to produce audio-frequency vibrations whose phases are displaced by 180 degrees across the joint flat portions 134, 144, 154 having a small mechanical strength. At this frequency, the acoustic signal generated from the dome portion and the acoustic signal generated from the edge portion are canceled with each other out so that a dip of a sound pressure occurs. In particular, when this dip of the sound pressure lies in an audible band, a quality of an acoustic signal is degraded.
In view of the aforesaid aspect, it is an object of the present invention to provide a speaker apparatus capable of eliminating vibrations of the dome portion and the edge portion with a phase difference of 180 degrees and which is capable of reproducing sounds of excellent quality of acoustic signals having high audio frequencies by increasing a strength of a flat joint portion and by properly setting a mass ratio between a dome-like diaphragm and an edge-like diaphragm of a speaker diaphragm.
According to an aspect of the present invention, there is provided a conductive type speaker apparatus in which a speaker diaphragm formed by joining a dome-like diaphragm and an edge-like diaphragm is actuated to vibrate by using a voice coil. This speaker apparatus is comprised of a diaphragm portion in which a mass ratio of the edge-like diaphragm relative to the dome-like diaphragm falls within a predetermined range near 1 and a fixed portion at which an end face of the voice coil bobbin is bonded to and fixed to a flat portion for joining the dome-like diaphragm and the edge-like diaphragm.
According to another aspect of the present invention, there is provided a conductive electromagnetic induction speaker in which a speaker diaphragm formed by joining a dome-like diaphragm and an edge-like diaphragm is vibrated by electromagnetic induction generated from a conductive one turn ring. This conductive electromagnetic induction speaker is comprised of a diaphragm portion in which a mass ratio of the edge-like diaphragm relative to the dome-like diaphragm falls within a predetermined range near 1 and a fixed portion at which an end face of the conductive one turn ring is bonded to and fixed to a flat portion for joining the dome-like diaphragm and the edge-like diaphragm.
In the speaker apparatus according to the present invention, a diaphragm of a conductive type speaker and a conductive type electromagnetic induction speaker is molded in such a manner that a mass ratio between the central dome-like diaphragm and the edge-like diaphragm falls within a range near 1, e.g., a mass ratio falls within a range of from 0.5 to 1.5. Further, since the end face of the voice coil bobbin or the end face of the conductive one turn ring is bonded to the flat portion which joints the central dome-like diaphragm and the edge-like diaphragm, a mechanical strength of the flat portion can be increased.
Therefore, according to the present invention, there can be obtained the following actions.
According to the speaker apparatus including the diaphragm portion comprised of the dome-like diaphragm and the edge-like diaphragm and the fixed portion bonded to and fixed to the coil bobbin or the conductive one turn ring and the flat portion, by increasing strength of the joint flat portions joining the dome-like diaphragm and the edge-like diaphragm the mechanical strength of which has been weak, vibrations of the dome-like diaphragm and the edge-like diaphragm with a phase difference of 180 degrees can be removed and sounds of high audio frequencies, e.g., sounds of high audio frequencies up to 50 kHz can be reproduced.